The neutron electric form factor to Q² = 1.45 (GeV/c)²

Abstract

The nucleon elastic electromagnetic form factors are fundamental quantities needed for an understanding of nucleon and nuclear electromagnetic structure. The evolution of the Sachs electric and magnetic form factors with Q 2 , the square of the fourmomentum transfer, is related to the distribution of charge and magnetization within the nucleon. High precision measurements of the nucleon form factors are essential for stringent tests of our current theoretical understanding of confinement within the nucleon.Measurements of the neutron form factors, in particular, those of the neutron electric form factor, have been notoriously difficult due to the lack of a free neutron target and the vanishing integral charge of the neutron. Indeed, a precise measurement of the neutron electric form factor has eluded experimentalists for decades; however, with the advent of high duty-factor polarized electron beam facilities, experiments employing polarization degrees of freedom have finally yielded the first precise measurements of this fundamental quantity.Following a general overview of the experimental and theoretical status of the nucleon form factors, a detailed description of an experiment designed to extract the neutron electric form factor from measurements of the neutron's recoil polarization in quasielastic 2 H(e, e')lH scattering is presented. The experiment described here employed the Thomas Jefferson National Accelerator Facility's longitudinally polarized electron beam, a magnetic spectrometer for detection of the scattered electron, and a neutron polarimeter designed specifically for this experiment. Measurements were conducted at three Q 2 values of 0.45, 1.13, and 1.45 (GeV/c) 2 , and the final results extracted from an analysis of the data acquired in this experiment are reported and compared with recent theoretical predictions for the nucleon form factors. Next, I would like to thank those who I credit most for my development: Jim Kelly and Andrei Semenov. At times, I found Jim's extremely high standards and desire for rigor to be exasperating, especially during the development of our simulation code and discussions of formalism (e.g., the "dreaded" Wigner rotation!), but, in retrospect, I am glad that I was constantly challenged to do something in an even better way and never permitted to give up. Indeed, I didn't fully appreciate the rigor of our analysis until our results were final, but hindsight is always 20/20. Also, I thank Jim for numerous comments and suggestions on this thesis; it is much better and much more complete because of his many suggestions. Andrei was the true guru (read: czar) of our analysis efforts, and he instilled in me the importance of careful work.I especially appreciate Andrei's timely responses to the numerous questions I always had concerning the analysis and the various analysis tools that we used; if there was someone who was sure to know the answer, that person was Andrei. Without Andrei, our analysis efforts would never have gotten off the ground. I also offer thank...